Cell Membrane Models and Transport Mechanisms
Membrane Models
1. Gorter and Grendel (1925): Extracted lipids from erythrocyte membranes. By calculating that spreading them on water resulted in twice the area that should be addressed by erythrocyte membranes, they concluded that the membrane is a bimolecular lipid layer.
2. Danielli and Davson (1935): Proposed a model of the plasma membrane structure in which proteins are located in the polar groups (hydrophilic) of the lipid bilayer. Their model included pores or channels in the membrane to explain
Read MoreUnderstanding the Nervous System and Brain Function
Membrane Potential and Neuronal Function
1. What is a Membrane Potential?
The membrane potential is the electrical charge of the inside of a cell relative to the outside of the cell.
2. What is the membrane potential at these stages?
- a. Rest: -70mV
- b. The end of Depolarization: +30mV
- c. The end of Repolarization: -70mV
- d. Hyperpolarization: More negative than -70mV
3. In a single round of the Sodium-Potassium pump, which elements (and how many) move through the plasma membrane?
3 sodium ions (Na+) move out,
Read MoreHuman Anatomy and Physiology: Key Concepts
Trachea and Cilia Function
What is the purpose of having C-shaped cartilages in the trachea? What about the cilia lining the inside of the tube?
C-shaped tracheal cartilages made of hyaline cartilage maintain the integrity of the airway. The inner lining of ciliated epithelium tissue reinforces the anterior and lateral sides of the trachea to protect and maintain the airway open. The cilia move back and forth to sweep the mucus upwards towards the throat.
Oxygen Transport: Respiratory and Circulatory
Read MoreHuman Placenta: Formation, Structure, and Function
The Placenta: Structure and Function
The placenta is composed of maternal and, especially, fetal tissues. The structure facilitates contact between maternal and fetal blood circulations across the largest possible area, while maintaining their independence, at least until delivery. The human placenta exhibits the following characteristics:
- Hemochorial: The egg implants in the uterine lining, with the trophoblast penetrating the endometrium to erode the endothelium of uterine vessels, establishing
Cardiac, Lymphatic, and Respiratory Systems
Explain: How Heart Muscle Fibers Contract and the Pacemaker’s Role?
Cardiac muscle also consists of sarcomeres containing alternating thick and thin filaments. The cells tend to contract rhythmically and spontaneously, but these contractions are synchronized by electrical signals produced by specialized, highly developed muscle fibers of the sinoatrial node. Cardiac muscle fibers are electrically interconnected links between cells located interspersed, which allows for coordinated contraction. Specialized
Read MoreCell Structure, DNA, and Cell Division: An Explanation
Cell Structure, DNA, and Cell Division
Interface: The stage of cellular development without division, where genetic material exists as chromatin. During division, the cell prepares by doubling its DNA and condensing its components into chromosomes.
DNA
DNA is formed by the union of nucleotides, which are composed of deoxyribose, an organic nitrogenous base, and a phosphate group.
DNA Structure
DNA consists of two polynucleotide chains linked together, complementary to each other through their bases.